Corey Powell (the newest writer at the time) started off splendidly in the factually fantastic Sleepless in Ponyville, developing Scootaloo’s character as well as Scootaloo’s relationship with Rainbow Dash, and it was her turn again in Just for Sidekicks. The idea of Spike petsitting the Mane Six’s pets was great and better with the the Cutie Mark Crusaders' randomness. Unfortunately, JfS contains one of the biggest flaws in the series: the incapability to characterize Spike consistently as a main character. Just like Owl's Well that Ends Well and Spike at Your Service, his characterization and character development are tossed out the window.

Various strengths include:

1. "Don't have your cake and it, too" was the main moral in this episode, but it was cleverly hidden in the canon despite the fact that it was in your face since the beginning. Instead of telling the moral, it was progressively shown in several basic steps. Show, don't tell.
   
2. The Cutie Mark Crusaders were brilliant. In her two episodes, they were written really well with intact, three-dimensional characterization. Sweetie Belle was cute as usual, and both Apple Bloom and Scootaloo are eager yet still different to where they're not carbon copies of each other.
   
3. The pets were absolutely great. Previously, the pets (minus some exceptions) tended to appear once or twice and then forgotten. This was the episode where they all shone, from Winona to Owlowiscious to Gummy to lovable Tank to the Angel from hell (who played his role as antagonist while not going overboard — and with good reasons — unlike his out-of-character behavior in Putting Your Hoof Down).
   
4. There's extremely dedicated kinship between the Mane Six and their pets. From the way they talked and behaved with their pets, it's obvious that they're extremely close. The cutest was Rainbow Dash and Tank and how Dash tried to hide it in her typical tomcoltish fashion. Cute and funny.
   
5. Angel's extreme suspicions with Spike. Since the beginning of the episode, he obviously didn't like the way Spike was handling himself and did whatever he could to embarrass the hell out of him and show to the Mane Six that he only took care of their pets for his own greed.
   
6. The little tidbits of Spike having to release Peewee back where he belongs. Through the pictures, Peewee was a great and troublesome little phoenix, yet still meant well. I'm glad he's back with his parents, but it's a little disappointing and unfortunate that we may likely never see him in the series again. (I hope FIM brings him back someday.)
   
7. The concept of the episode was simple, but fits the scope of My Little Pony: Friendship Is Magic very well.
   
8. The background ponies are back again, which is good because without background characters, regardless of the beautiful graphics, the atmosphere is dead. With them showing up, it gave Ponyville, the Friendship Express, and Crystal Empire station life. The world of MLP:FIM needs that to engage itself to the audience.
   
9. The pace was so smooth here. It flowed from one scene to the next without any need to rush, a role reversal from Keep Calm and Flutter On, Spike at Your Service, Games Ponies Play, Magical Mystery Cure, and Equestria Girls.
   
10. Just like Keep Calm and Flutter On, there were layers of foreshadowing throughout to hint where the episode would travel and resolve. Four big clues include the cake, Angel’s attitude, Spike giving away the jewels one by one, and Zecora warning him in her usual rhyming self to not lust for his delicious jewels.
    
11. Hey, look! Spike’s ability to cook was back! Unfortunately, his continuous appetite for jewels bit him… Thankfully, unlike his out-of-character incompetence in Spike at Your Service, he actually wasn’t aloof, careless, or stupid in handling things. He knew right away he messed up and decided to fix it.
    

Unfortunately, there are three key problems.

1. Fluttershy was out of character in the beginning. While it made sense for her (and the others) to exchange gems to Spike in exchange for him petsitting, the way she did it was very off-putting: the transparent way she manipulated and convinced him to petsit Angel. Keep Calm’s method of manipulating Discord into eating his own words was extremely intelligent, clever, and hidden. It was a great twist. Here, it was very inorganic. If the approach was softer and didn’t intentionally tug Spike’s greed, then it might’ve gotten somewhere.
   
2. Equestria’s geography and sense of time (from a writing perspective) are very disorganized (a common issue in the series), and there is no railway realism. The Crystal Empire and Ponyville are presumably separated by at least several hundred miles. From the way the script was written, the trip lasted a couple of hours to the Empire and then back, as it was still daylight out there. No saddle tank engine (especially one that size) would travel this far for this long without a stop at the station, switch of trains, and visit to the water tower to fill up the tank and/or coal hopper to refill the bunker. And the train ride would definitely not make a round trip this quickly within a day, either.
   
3. Spike himself was completely unrecognizable. Just like Spike at Your Service, the Spike featured on the screen in JfS wasn’t Spike, but rather an imposter. Besides his ability to cook and grouse after realizing he wasn’t invited to the Equestria Games, his characterization and development from the rest of series were nonexistent.
    
   Instead of being completely careless in every single thing he did like in Spike at Your Service, this drastic bastardization in his character shifted to the other side of the scale. He was greedy, selfish, and manipulative; he didn't care about the pets at all. Instead of a balance between selfishness and selflessness throughout, it was segregated, with his selfishness used as a headache-inducing comedic plot device for almost the entire episode until the very end. He took advantage of his friends (as well as their trust for him) and used their pets as pawns to make his jewel cake.
    
   In season two, the two episodes starring him included two huge facets that helped him grow into a much more selfless character:
    
   a. In Secret of My Excess, we saw how much greed in a dragon can consume his or her soul. Spike since learned about the dangers of greed.
    
   b. In Dragon Quest, Spike wanted to find his own in the dragon world, so he joined the migration, where he bumped into some very antagonist, one-dimensional teenaged dragons. But here, he also learned about how precious life and caretaking were when he refused to destroy the phoenix egg. He wasn't going to give in to peer pressure from other dragons. Even in his short time, it's obvious he cared so much for Peewee.
    
   It's particularly the absence of his development from Dragon Quest where there was such a big problem here. He wasn't going to sacrifice anyone's lives for the sake of sticking with the clan. But he also knew that being someone's caretaker required massive responsibilities, and Spike is someone who can hold his own despite messing up occasionally. For example, in Magic Duel, he was the one who kept the team together while Twilight was exiled in the Everfree Forest. It was a small scene quantitatively, but it gave him so much depth in his character. Here, he showed no care for the pets at all, a complete contradiction of Dragon Quest's resolution/moral and his affection and love for Peewee himself. This is a task that requires so much trust, and Spike give no damn about what they were thinking until the very end. He came across as antagonistic, making him an unlikeable, out-of-character shell.
    
   Even with a jewel cake that he would so love to bake, he knows very well that petsitting is a heavy responsibility, particularly at this stage of the series. What an in-character Spike would REALLY do is put the cake business beside him and take care of the pets while they're gone. And he (and maybe Owlowiscious) would be the ones disciplining the pets, especially Angel, whose trust for Spike and the other pets are thinner and more fragile than the graphite of a mechanical pencil. He may retain those thoughts about the cake, which would create conflict, but he'll promise to himself that he'll take his time disciplining the pets and sacrifice his cake willingly. Once he's done, then maybe he'll get jewels as a reward, and maybe he can successfully bake his cake (attempting to taste a jewel, but warned by Owlowiscious before he does), or he chooses not to bake it voluntarily. That way, the moral of "don't have all of your cake and eat it, too" can still fit yet keep Spike in character.
    
   Frankly, this would have been much better if it were a season one or season two episode (pre-SoME or pre-DQ), where he wasn't given a lot of development and still had that extremely selfish streak in him. But it took place late in season three, and he received so much character development since the premiere. Therefore, it stuck out and just didn't fit him. This growth of his personality was absent in Just for Sidekicks.
   

Spike is a character with several important roles in Season 3. Despite being minute, they helped him grow as a more mature character. To see that growth reversed in this season’s two Spike-centered episodes is a huge disappointment. It's an even bigger disappointment here because Powell is an excellent writer with Emmy Award nominations to her credit. I've seen her work, so she has the experience and wherewithal to do so great. Sleepless in Ponyville is one of the best episodes in the entire series and was an amazing debut. She showed exactly what she could do there and even here in many places. To see that potential fall flat with an out-of-character Spike in Just for Sidekicks is unfortunate.

This was an episode with both a great concept and moral, and it was filled with so much potential. The Cutie Mark Crusaders and the pets were filled with character that resulted in plenty of laughs and conflict. But Spike was the focus in Just for Sidekicks, and he was extremely poorly written. One of the biggest reasons Spike at Your Service was bad was because he was written as carelessly incompetent, but even there did he show plenty of care for others. Here, his extreme selfishness and lust for a jewel cake were a sudden flip of his character development, and he didn't behave like Spike one damn bit. Overall, the third-worst episode in Season 3 and my most hated FIM episode overall.